1. Technical Field of the Invention
The present invention relates to a reciprocating pump for sucking and discharging a fluid by means of a reciprocating member such as a piston, a plunger, etc., and in particular to a reciprocating pump provided with malfunction-detecting means for detecting malfunctions or abnormalities, such as sucking failure, and failure to discharge a fluid under pressure up to a destination.
2. The Related Art
An ordinary reciprocating pump to be employed for the lubrication of a small air-cooled two-stroke gasoline engine (hereinafter, referred to as an internal combustion engine) which is adapted to be employed as a power source for a portable power working machine, such as a chain saw, is constructed as shown in FIG. 11, for instance. This conventional reciprocating pump shown in FIG. 11 will be briefly explained as follows. The reciprocating pump 2 basically comprises a main body 60 in which a cylinder portion 65, provided with awl sucking port 66 and an discharging port 67 to be opened or closed by a ball valve 75, is fittingly received, a reciprocating member 70, comprising a plunger rod 71 slidably fitted in the cylinder portion 65 and a main plunger body 72 into which a rear end portion of the plunger rod 71 is press-inserted and fixed thereto, a solenoid 80 attached to one end portion (on the right side in the drawing) of the main body 60 so as to drive the reciprocating member 70, and a delivery passageway member 90 screw-engaged with the other end portion (on the left side in the drawing) of the main body 60.
The ball valve 75 is normally urged in the direction to close the discharging port 67 by means of a coil spring 74 which is interposed between the ball valve 75 and the delivery passageway member 90. On the other hand, the reciprocating member 70 is normally urged toward the right side of the drawing by means of a coil spring 78 which is interposed between the cylinder portion 65 and the main plunger body 72.
The solenoid 80 is secured between the main body 60 and a securing tube body 84 which is screw-engaged with the outer circumferential wall of one end of the main body 60. The outer circumferential wall of the securing tube body 84 is encased by a stopper cover 85 having a bottomed cylindrical configuration.
The solenoid 80 is designed to be switched ON (electrical magnetization)/OFF by way of a driving pulse to be fed thereto at a predetermined cycle from an outside power source (controlling device) (not shown). When the solenoid 80 is switched OFF from ON, the reciprocating member 70 is caused to move rightward in the drawing due to the urging force of the coil spring 78, thereby moving the plunger rod 71 in the direction to open the sucking port 66. As a result, a fluid (a lubricating oil for the internal combustion engine) is permitted to flow into a valve chamber 61 which is formed between the plunger rod 71 and the ball valve 75, and, at the same time, the rear flange portion 73 of the main plunger body 72 is contacted with the stopper cover 85 (the state indicated by a solid line in the drawing).
When the solenoid 80 is switched ON in this state, the reciprocating member 70 is caused to move leftward in the drawing due to the generation of magnetic force, thereby moving the plunger rod 71 in the direction to close the sucking port 66, and, at the same time, the fluid in the valve chamber 61 is pressed so as to push the ball valve 75 leftward in the drawing. As a result, the flange portion 73 of the main plunger body 72 contacts a plastic buffer plate 88 adhered to the right end face of the securing tube body 84.
As a result, the discharging port 67 is opened, thus permitting the fluid in the valve chamber 61 to flow toward the delivery passageway member 90.
Therefore, it is possible, through the ON/OFF operation of the solenoid 80, to enable the lubricating oil in an oil tank (not shown) to be introduced, through an oil strainer and an inlet pipe, etc. (not shown), into the valve chamber 61 from the sucking port 66. The lubricating oil thus introduced into the valve chamber 61 is then permitted to flow therefrom in a pressurized manner so as to be delivered, through the discharging port 67, the ball valve 75, a delivery passageway 92 extending through the delivery passageway member 90, a check valve 95 disposed at the delivery port of the delivery passageway 92, and an discharge pipe (not shown) coupled with the delivery passageway member 90, to the destination, i.e. the sliding portions of the internal combustion engine, etc.
The reference number 68 in FIG. 11 represents a space for introducing the power cables (not shown) for feeding a driving pulse to the solenoid 80.
If any operational abnormality occurs in the reciprocating pump described above, e.g. the sucking side of the pump is clogged, i.e. the oil (fluid) can no longer be normally sucked due to the exhaustion of oil (due to the sucking of air), or a clogging of the pipe at the discharge port is generated to thereby make it impossible to feed the oil to the destination thereof it is desirable to take any appropriate countermeasure, such as to stop the internal combustion engine to prevent seizure, or to give an alarm.
Therefore, it is conventionally considered to attach a pressure sensor to the reciprocating pump so as to detect a fluctuation of pressure at the discharge port. In this case, the aforementioned abnormality can be detected based on an output (detection signal) emitted from the pressure sensor.
More specifically, as shown in FIG. 11 for instance, a take of port 97 is installed to the delivery passageway member 90 so as to introduce, via a rigid pipe 98 for instance, a portion the oil existing at the discharge port (a delivery pressure) into a pressure sensor 100 to thereby detect a fluctuation of pressure at the discharge port.
For this purpose, a pressure sensor 100 of intermediate conversion type, which is designed to pick up all electric signal after converting the discharge pressure of oil into another kind of physical quantity (such as the magnitude of displacement) by making use of a diaphragm, etc., is generally employed. For example, a sensor wherein a strain gage is adhered onto a diaphragm, a sensor wherein a coil and a core are symmetrically arranged on both sides of a magnetic diaphragm so as to constitute an equilibrium magnetic circuit, and a sensor wherein a conductive diaphragm and an electrode are arranged to face each other so as to constitute a pair of capacitors are available in the market.
In this case, the output of the pressure sensor 100 changes synchronously with the ON/OFF operation (the discharging and sucking operation by the reciprocating member 70) of the solenoid 80 as shown in FIGS. 12(A) to 12(C). Namely, when the oil is normally supplied without any aforementioned abnormalities, the output of the pressure sensor 100 becomes wavy as shown in FIG. 12(A). When the oil is exhausted, e.g., clogging of the sucking side of the pump, the timing of discharging a change in output from that of the normal operation lags slightly behind (due to the entrainment of air) and at the same time, the amplitude of the output is slightly reduced as shown in FIG. 12(B). When the clogging of oil is caused to occur on the discharge side, the output of the pressure sensor 100 is extremely increased (becomes very high) as shown in FIG. 12(C). Therefore, it becomes possible, through the processing of the output (detected signals) of the pressure sensor 100, to detect the type of abnormality that has occurred.
The pressure sensors that are generally available in the market as mentioned above however are somewhat expensive if they are to be employed as detecting means for detecting abnormalities, such as the exhaustion of oil or the clogging of oil on the discharge side, of a reciprocating pump to be employed for the lubrication of an internal combustion engine which is designed to be employed as a power source for a portable working machine such as a chain saw. In addition to that, it is also required in the case of the aforementioned pressure sensors to introduce a fluid such as oil (a discharge pressure) directly into the pressure sensors, thereby raising a problem of the space for mounting such an introducing means. Therefore, as a matter of fact, it has been very difficult to mount any of the aforementioned pressure sensors on the reciprocating pump.
The present invention has been made with a view to overcoming the aforementioned problems. It is therefore an object of the present invention to provide a reciprocating pump, which is capable of reliably detecting abnormalities in the sucking and discharging of fluid, such as the exhaustion of oil or the clogging of oil on the discharge side, by making use of detecting means which is inexpensive and relatively simple in structure, the detection by the detecting means being enabled to execute without being unduly influenced by the bubbles included in the fluid and without allowing noise to be generated by external vibrations, thus making it possible to enhance the reliability and accuracy in the detection of abnormalities, the reciprocating pump being further featured in that it is capable of reliably preventing problems such as the leakage of fluid outside the pumping system.
In furtherance of the aforementioned objects, the present invention provides, as a first embodiment, a reciprocating pump for sucking and discharging fluid by making use of a reciprocating member, which pump, for the purpose of detecting abnormalities, if any, in the sucking and discharging of fluid, includes an abnormality-detecting means formed of a piezoelectric element for detecting a pressure fluctuation on a discharge side of the pump.
The piezoelectric element is preferably of ring-like or cylindrical configuration and is externally fitted on an outer wall of a delivery passageway member which constitutes a fluid discharge side of the pump.
In a preferred embodiment, the reciprocating pump according to the first embodiment comprises a main body having a cylinder portion provided with an sacking port and with an discharging port to be opened or closed by a valve, a reciprocating member reciprocatively fitted in the cylinder portion to thereby enable a fluid to be sucked through the sucking port and to enable the fluid thus sucked to be discharged from the discharging port toward a delivery passageway, and a solenoid for driving the reciprocating member.
In this case, the piezoelectric element is fitted on an outer wall of a delivery passageway member and sustained between a flange portion of the delivery passageway member and the main body. Preferably, an sucking member is interposed between the piezoelectric element and the delivery passageway member and between the piezoelectric element and the main body.
The reciprocating pump according to the first embodiment of the present invention is suited for use as an oil pump wherein a fluid to be sucked and discharging is a lubricating oil for an internal combustion engine.
In another preferred version of the reciprocating pump according to the first embodiment of the present invention which is constructed as mentioned above, a single body of the piezoelectric element having a ring-like or cylindrical configuration is employed as an abnormality-detecting means for detecting abnormalities, if any, in the sucking and discharging of fluid. In a preferable embodiment, the piezoelectric element is externally fitted on an outer wall of a delivery passageway member and sustained between a flange portion of the delivery passageway member and the main body, with an sucking member being interposed between the piezoelectric element and the delivery passageway member, and between the piezoelectric element and the main body.
According to the reciprocating pump of the present invention which is constructed as mentioned above, the delivery passageway member is caused to expand or shrink, for instance, due to a fluctuation of pressure of the fluid existing on the discharge side of the fluid to be sucked and discharged by the reciprocating pump, a force resulted from the deformation of the delivery passageway member is transmitted via the insulating member to the piezoelectric element. As a result, the piezoelectric element is caused to expand or shrink, and hence the output (detected signals) from the piezoelectric element is caused to change depending on the aforementioned fluctuation of pressure.
In this case, the output from the piezoelectric element becomes essentially identical with the output of the aforementioned pressure sensor, so that when the output from the piezoelectric element is processed by means of a computer, etc, the type of the abnormality, such as the exhaustion of oil or the clogging of oil, can be automatically detected.
A piezoelectric element of ring-like or cylindrical configuration as described above is available in the market at a considerably lower price than the aforementioned conventional pressure sensor. Additionally, it is not necessary to introduce a fluid such as oil (discharge pressure) directly into the piezoelectric element. Moreover, the ring-like or cylindrical piezoelectric element can be easily fitted on the outer wall of the delivery passageway member and sustained between the delivery passageway member and the main body, thereby making it possible to extremely simplify the attachment of the piezoelectric element.
As described above, it is possible according to the first embodiment of the present invention to reliably detect abnormalities in the sucking and discharging of fluid, such as the exhaustion of oil or the clogging of oil on the discharge side, by making use of an inexpensive piezoelectric element which is also relatively simple in structure.
On the other hand, in a second embodiment of the reciprocating pump according to the present invention, the pump is constructed such that a pressure fluctuation of the fluid being discharged from the discharging port can be directly transmitted to the piezoelectric element employed as an abnormality-detecting means.
In this case, the delivery passageway member communicated with the discharging port is preferably formed into a cylindrical configuration having a passageway/pressure detecting chamber incorporated therein, and also having the piezoelectric element secured to the outer circumferential wall thereof.
In a more preferable embodiment, the reciprocating pump comprises a main body having a cylinder portion provided with an sucking port and with an discharging port the, delivery passageway member communicated via a first pressure-adjusting valve with the discharging port of the main body, a second pressure-adjusting valve disposed on a downstream side of the delivery passageway member, a reciprocating member reciprocatively fitted in the cylinder portion to thereby enable a fluid to be sucked through the sucking port and enable the fluid thus sucked to be discharged from the discharging port toward the passageway/pressure detecting chamber, and a solenoid for driving the reciprocating member, wherein the pressure adjustment valve of the second pressure-adjusting valve is set higher than the pressure adjustment valve of the first pressure-adjusting valve, and a pressure fluctuation of the fluid inside the passageway/pressure detecting chamber is enabled to be directly transmitted to the piezoelectric element.
According to this second embodiment of the reciprocating pump constructed as described above, since a pressure fluctuation of the fluid being discharged from the discharging port can be directly transmitted to the piezoelectric element, the reaction of the piezoelectric element to a pressure fluctuation of the fluid is rendered more sensitive as compared with the aforementioned first embodiment, wherein the deformation force due to the expansion and shrinkage of the delivery passageway member is designed to be transmitted to the piezoelectric element, i.e. wherein a pressure fluctuation of the fluid is indirectly transmitted to the piezoelectric element.
Further, in the previous embodiment where the piezoelectric element having a ring-like or cylindrical configuration is externally fitted on an outer wall of the delivery passageway member, there is a possibility that the fluctuation of pressure of fluid might be absorbed by a flexible hose connected with the delivery passageway member, so that the fluctuation of output of the piezoelectric element could be rather weak and small. Whereas, in this second embodiment, since the second pressure-adjusting valve is mounted on the delivery passageway member in addition to the first pressure-adjusting valve (which is generally provided as a discharge valve) so as to enable a pressure fluctuation of the fluid existing between these valves to be directly transmitted to the piezoelectric element, the sensitivity of the piezoelectric element to a pressure fluctuation of the fluid can be further enhanced.
Therefore, it is possible, according to this second embodiment, to improve the reliability and accuracy in the detection of abnormality of the pump, thus enhancing the reliability of the pump.
Furthermore, with a view to attaining the aforementioned objects, according to a third embodiment of the reciprocating pump of the present invention, an abnormality-detecting means formed of a piezoelectric element for detecting a pressure fluctuation on a discharge side of the pump is attached to the pump in order to detect any abnormality in the sucking and discharging of fluids wherein a pressure fluctuation of the fluid being discharged from the discharging port can be directly transmitted to the piezoelectric element through a pressure-receiving member made of a rigid body.
In a preferable embodiment, the delivery passageway member communicated with the discharging port is preferably formed into a cylindrical configuration having a passageway/pressure detecting chamber incorporated therein and also having the piezoelectric element secured to the outer circumferential wall thereof.
In a more preferable embodiment, an insert hole for slidably fitting the pressure-receiving member therein is formed between the passageway/pressure detecting chamber and the piezoelectric element to enable the fluctuation of pressure of fluid inside the passageway/pressure detecting chamber to be transmitted to the piezoelectric element.
The pressure-receiving member is preferably shaped into a T-shaped configuration in side view, which is constituted by a rod-like insert portion and a disc-like pushing portion.
In another preferable embodiment, a doughnut-shaped sealing member is externally inserted over the rod-like insert portion of the pressure-receiving member and positioned in contact with the disc-like pushing portion so as to seal an interface between the passageway/pressure detecting chamber and the piezoelectric element.
In another preferable embodiment, a vibration-proofing member made of rubber, etc. is interposed between the delivery passageway member and the piezoelectric element in order to prevent external vibrations from being transmitted to the piezoelectric element.
According to this third embodiment of the reciprocating pump constructed as described above, since a piezoelectric element is employed as an abnormality-detecting means for detecting any abnormality in the sucking and discharging of fluid, and a pressure fluctuation of the fluid being discharged from the discharging port is enabled to be directly transmitted to the piezoelectric element through a pressure-receiving member made of a rigid body, the piezoelectric element is caused to expand or shrink as it is directly pushed by the pressure-receiving member in conformity with the fluctuation of pressure of the fluid, thereby enabling the output of the piezoelectric element to fluctuate in conformity with the fluctuation of pressure. In this case, the output of the piezoelectric element is fundamentally the same as the output of the aforementioned conventional pressure sensor. Therefore, it becomes possible, through the processing of the output of the piezoelectric element by making use of a computer, etc., to automatically detect the type of the aforementioned abnormality, such as the exhaustion of oil or the clogging on the oil discharge side. In this case, since the piezoelectric element is available in the market at considerably low price as compared with the aforementioned pressure sensor, it is possible to reliably detect abnormalities in the sucking and discharging of fluid, such as the exhaustion of oil or the clogging of oil on the discharge side, by making use of an inexpensive and structurally simple piezoelectric element.
Additionally, since the fluctuation of pressure of fluid is transmitted to the piezoelectric element through a pressure-receiving member made of a rigid body, it is possible to greatly enhance the reliability and accuracy in the detection of abnormality as compared with those to be obtained by the reciprocating pump of the aforementioned second embodiment wherein the fluctuation of pressure of fluid is designed to be transmitted to the piezoelectric element possibly through a fluid containing air bubbles of the pressure transmitting passageway portion.
Since a vibration-proofing member made of rubber, etc. is interposed between the delivery passageway member and the piezoelectric element, external vibrations due to the reciprocative movement of the reciprocating pump (main body) or of the internal combustion engine to which the fluid (lubricating oil) is to be fed can be absorbed and alleviated by the vibration-proofing member, thus making it possible to inhibit the external vibrations from being transmitted to the piezoelectric element. As a result, it is possible to minimize the noise originating from such external vibrations, thereby making it possible, for this reason also, to enhance the reliability and accuracy in the detection of abnormality.
Additionally, since a doughnut-shaped sealing member is externally inserted over the rod-like insert portion of the pressure-receiving member and positioned in contact with the disc-like pushing portion, it is possible to prevent the sealing member from being undesirably deformed (deformation such as the narrowing of the inner diameter thereof) by the effects of the fluctuating pressure of fluid as seen in the case of the aforementioned second embodiment, thereby making it possible to prevent the leakage of fluid out of the pumping system.